1. Field of the Invention
This invention generally relates to large caliber ammunition and more particularly to armor penetrating, fin stabilized discarding sabot (APFSDS) projectile cartridges.
2. Discussion of the Related Art
A large caliber APFSDS cartridge typically has a combustible case attached to a saboted long rod penetrator. The sabot has a front bore riding support or bourrelet and a rear bore riding support or bourrelet. The case is attached to the aft bourrelet on the sabot. The aft bourrelet is a solid cylindrical portion that forms a closure on the case mouth, thus retaining the propellant in the case. The front bourrelet is spaced from the case mouth and includes a scoop to catch onrushing air upon projectile exit from the gun tube. The scoop shaped front bourrelet permits onrushing air to separate the segments of the sabot from the fin stabilized long rod penetrator. The Propelling gases push against the aft face of the aft bourrelet to Push the projectile through the tube. When such a cartridge is inserted in the gun chamber, there is a toroidal void formed between the front and aft bourrelets and the inside surface of the gun tube. This void conventionally serves no useful function.
U.S. Pat. No. 4,964,342, issued to Schleicher on Oct. 23, 1990, discloses a sabot arrangement for an APFSDS projectile having front and aft bourrelets which has passages through the aft bourrelet. The passages through the aft bourrelet permit propelling gases to act upon the rear face of the front bourrelet to pull the saboted Projectile through the gun tube.
U.S. Pat. No. 4,974,517, issued to Kraft et al on Dec. 4, 1990, discloses an APFSDS round with passages through the aft bourrelet connecting the space between the bourrelets with the propellant case. A combustible, or thin rupturable barrier separates the propellant in the case from the passage into the void between the bourrelets.
U S. Pat. No. 4,936,220, issued to Burns et al on Jun. 6, 1990, discloses a saboted projectile having a scoop front bourrelet and a cylindrical rear bourrelet with a tubular sleeve between them made of a combustible material. Several plugged through bores through the aft bourrelet connect the toroidal cavity between the bourrelets with the rear face of the aft bourrelet. A portion of the propelling charge is contained within the toroidal cavity. This portion of the charge is sequentially ignited after ignition of the main charge by an igniter mounted in an unsealable blowout plug in the through bore or a delay charge/seal positioned in each of the through bores. The concept here is to sustain the pressure Peak as the propelled projectile moves through the gun tube by providing a delayed ignition of an additional charge.